---
name: "Graph::AdjacencyMatrix"
section: "3pm"
platform: "linux"
package: "libgraph-perl"
version: "1:0.9735-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/Graph::AdjacencyMatrix"
---

# Graph::AdjacencyMatrix(3pm)

create and query the adjacency matrix of graph G

## NAME

Graph::AdjacencyMatrix - create and query the adjacency matrix of graph G

## SYNOPSIS

```
    use Graph::AdjacencyMatrix;
    use Graph::Directed; # or Undirected
    my $g  = Graph::Directed->new;
    $g->add_...(); # build $g
    my $am = Graph::AdjacencyMatrix->new($g);
    $am->is_adjacent($u, $v)
    my $am = Graph::AdjacencyMatrix->new($g, distance_matrix => 1);
    $am->distance($u, $v)
    my $am = Graph::AdjacencyMatrix->new($g, attribute_name => 'length');
    $am->distance($u, $v)
    my $am = Graph::AdjacencyMatrix->new($g, ...);
    my @V  = $am->vertices();
    $g = Graph->new(multiedged => 1);
    $g->add_...(); # build $g
    $am = Graph::AdjacencyMatrix->new($g, distance_matrix => 1);
    $am->distance($u, $v) # returns hash-ref of ID => distance
```

## DESCRIPTION

You can use `"Graph::AdjacencyMatrix"` to compute the adjacency matrix and optionally also the distance matrix of a graph, and after that query the adjacencyness between vertices by using the `is_adjacent()` method, or query the distance between vertices by using the `distance()` method.

By default the edge attribute used for distance is `"w"`, but you can change that in **new()**, see below.

If you modify the graph after creating the adjacency matrix of it, the adjacency matrix and the distance matrix may become invalid.

## Methods

### Class Methods

- new($g)

  Construct the adjacency matrix of the graph `$g`.

- new($g, options)

  Construct the adjacency matrix of the graph `$g` with options as a hash. The known options are

  - distance\_matrix =\> boolean

    By default only the adjacency matrix is computed.  To compute also the distance matrix, use the attribute `"distance_matrix"` with a true value to the **new()** constructor.

  - attribute\_name =\> attribute\_name

    By default the edge attribute used for distance is `"w"`.  You can change that by giving another attribute name with the `"attribute_name"` attribute to **new()** constructor.  Using this attribute also implicitly causes the distance matrix to be computed.

### Object Methods

- is\_adjacent($u, $v)

  Return true if the vertex `$v` is adjacent to vertex `$u`, or false if not.

- distance($u, $v)

  Return the distance between the vertices `$u` and `$v`, or `"undef"` if the vertices are not adjacent.

  If the underlying graph is multiedged, returns hash-ref of ID mapped to distance. If a given edge ID does not have the attribute defined, it will not be represented. If no edge IDs have the attribute, `"undef"` will be returned.

- adjacency\_matrix

  Return the adjacency matrix itself (a list of bitvector scalars).

- vertices

  Return the list of vertices (useful for indexing the adjacency matrix).

## ALGORITHM

The algorithm used to create the matrix is two nested loops, which is O(V\*\*2) in time, and the returned matrices are O(V\*\*2) in space.

## SEE ALSO

Graph::TransitiveClosure, Graph::BitMatrix

## AUTHOR AND COPYRIGHT

Jarkko Hietaniemi *jhi@iki.fi*

## LICENSE

This module is licensed under the same terms as Perl itself.